Signification of the unusual delineation of the anterior meniscofemoral ligament of Humphrey during knee arthro-CT

Background Meniscofemoral ligaments (MFLs) are recognized as stabilizing and protective structures for the posterolateral meniscocondylar compartment of the knee, and as secondary restraints to tibial posterior translation. Purpose and patients We report the 64-row arthro-MDCT findings of 10 patients ( 8 males, 2 females; mean age 43.8 years) in which the anterior MFL of Humphrey (aMLF) was atypically well delineated by an unusual circumferential effusion of iodine contrast. We discuss a possible physiopathologic mechanism for this effusion, describe the MDCT anatomy of the aMLF and review the literature about the anatomy and physiology of the MFLs. Results In each of our ten patients an unusual effusion of articular contrast was found delineating a posterior oblique ligamentar bundle, which was running in front of the posterior cruciate ligament (PCL). This bundle was best appreciated on posterior coronal oblique and sagital MPR views, and was recognized as the aMFL. The finding was associated with a partial tear of the tibial insertion of the posterior horn (PH) of the lateral meniscus (LM) in three patients, and with a partial (two cases) or subtotal (three cases) tear of the PCL in five patients. A swollen-probably oedematous-PCL was found in another patient and in the last case the anomaly was minimal and remained isolated. All patients were treated conservatively. Conclusion Since the aMFL inserts inferiorly into the posterior horn of the LM and runs in very close anatomic and functional relation with the PCL, we hypothesize that a trauma producing a tear in these structures may also occasionally sufficiently stretch the aMFL to produce a peripheral loosening allowing a circumferential effusion of opacified synovial fluid around the ligament. Our report offers the opportunity to illustrate the "in vivo" anatomy of the aMFL through original unpublished figures. It also contributes to reinforce the literature data concerning the potential fine mechanical role played by the LM-MFLs-PCL complex, in which the centrally located MFLs act laterally as stabilizing and protective structures for the posterolateral meniscocondylar compartment and medially as secondary restraints to tibial posterior translation.